The calculator has a stack that can contain real numbers.
• The calculator waits for user input and expects to receive strings containing whitespace separated lists of numbers and operators.
• Numbers are pushed on to the stack. Operators operate on numbers that are on the stack. • Available operators are +, -, *, /, sqrt, undo, clear.
• Operators pop their parameters off the stack, and push their results back onto the stack.
• The ‘clear’ operator removes all items from the stack.
• The ‘undo’ operator undoes the previous operation. “undo undo” will undo the previo us two operations.
• sqrt performs a square root on the top item from the stack.
• The ‘+’, ‘-’, ‘*’, ‘/’ operators perform addition, subtraction, multiplication and division respectively on the top two items from the stack.
• After processing an input string, the calculator displays the current contents of the stack as a space-separated list.
• Numbers should be stored on the stack to at least 15 decimal places of precision, but displayed to 10 decimal places (or less if it causes no loss of precision).
• All numbers should be formatted as plain decimal strings (ie. no engineering formatting).
• If an operator cannot find a sufficient number of parameters on the stack, a warning is displayed: operator (position: ): insufficient parameters
• After displaying the warning, all further processing of the string terminates and the current state of the stack is displayed.
- I was trying to be as expressive in code as possible, by naming things according to domain terms and project
requirements like:
SorryCannotFindSufficientNumberOfParametersInTheStack,Operation.performOperationAndAddResultToStack(), etc., to make the code as clear as possible for those who understand the domain - I was trying to follow Hexagonal/DDD approach, by splitting the whole project to
domain,applicationandinfrastructurelayers infrastructurelayer contains only CLI interface, but later on — will be able to support also web interface- All the calculator logic is contained in the
domainlayer, and adding a new operation shall not involve anything fromapplicationorinfrastructurelayers
git clone git@github.com:ibudasov/rpn-calculator.git
MainKt.main 👈 run it in your IDE 💁
- preserve stack between inputs, so the operations can be chained